The invention is based on an electromagnetic active brake, for example a sliding caliper brake, which in the brake standby state, thus in the open state, is de-energized.
In order to avoid disadvantages connected to the use and securing of pneumatic or hydraulic energy, instead of pneumatic and hydraulic brake systems, electromagnetic brake systems are used in combination with springs. For example, it is already known for drives of overhead garage doors with an electric linear motor to use a sliding caliper brake for braking the transmission rod of the linear motor, which is pre-loaded in the engaged state. The free ends of the brake shoes are connected to the housing and/or the driven part of an electromagnet, with its armature being pre-loaded by a spring in the inward direction such that the brake pads in the idle state tightly contact at the side areas of the transmission rod. When the electromagnet is energized the brake pads are lifted off the transmission rod (DE G 83 08 714.1). This brake arrangement is advantageously applied where the operating condition is overwhelmingly in the static state, thus the brakes actively contact the parts to be braked, in the present case therefore they are de-energized and due to spring force they are in the brake position. Only for a relatively short period, here during the opening or closing of the garage door, they are released by an electric pulse. For a brief braking process, parts that are overwhelmingly in motion are not suitable for this technical solution, because in order to keep the brake open in the break readiness position energy must constantly be applied to the electromagnet, which results in high energy consumption.
It is further known to use a sliding caliper brake with a fixed and a mobile friction brake coating and an electro-mechanic actuator device for pushing its mobile friction brake coating against a brake disk. It comprises a device for adjusting the clearance with a helical compression spring, which axially impinges a tappet and resets the brake caliper when releasing the sliding caliper brake and this way it adjusts a clearance between the friction brake coatings and the brake disk at both sides of said brake disk (DE 10 2006 018 953 A1). The disadvantage of this sliding caliper brake is given in that the electromagnetic actuator device, which generally represents an electric engine, performs both the braking actions as well as the release of the brake, thus requires electric energy for both processes. Additionally, the torque of the electric engine must be converted via a transmission into a useable actuating moment. The electric engine and the transmission enlarge the design and increase the production costs of the sliding caliper brake.
The clasp brake, also de-energized in the braking state, comprising an automatic adjustment in case of the brake pad wearing down, is characterized in that for retightening a pre-loaded spring an additional path is used which the brake pads must travel for contacting the part to be braked after exceeding an adjustable wear tolerance limit, in addition to the previously set path. During the release of the brake the force of the pre-loaded spring is released by an energized electromagnet compressing the brake compression spring and, via a now engaging freewheel and/or via restressing elements, for example an eccentric shaft or nut sheath, the distance of the brake lever bearings is reduced in reference to each other such that the contacting path of the brake pads is shortened and thus the wear is compensated (DE 10 2008 015 743 A1).
A parking brake that is very compact and failsafe, and exhibits a largely wear-independent braking effect for fixing a rotary braking motion, comprising two brake pads, which can be actuated via a brake clasp. The arms of the brake clasp are connected via an actuator to a compression spring and the actuator in turn via a transmission lever to the armature of an electromagnet. In the de-energized state the spring presses the two brake pads against the part to be braked. For releasing the brake pads the electromagnet is energized, causing its armature to be moved towards the armature endplate and here pulling back the armature pin via the transmission lever of the actuator against the spring acting upon it such that the tension spring arranged between the brake arms pivots the two brake arms in the sense of disengaging the brake (DE 103 15 985 A1).
In these two technical solutions the disadvantage is given in the limitation of the application to such aggregates, machine parts, or transportation devices, which during their operating state must be frequently or regularly braked, such as escalators, elevators for persons or freight, rotating or translationally moving machine parts, and thus the active braking process must be performed in the de-energized state in order to allow failsafe braking even when the power supply is interrupted.
Further known is an emergency brake for a passenger conveyance system, for example an escalator, which at any time provides a braking force proportional to the load conveyed. In the operating state an electromagnet keeps the brake pads from engaging the brake disk. Pressure pistons connected to the electromagnet engage brake levers connected to the brake pads. The brake levers are additionally connected to adjustable compression springs, with their spring force being adjustable depending on the load of the conveyance system using a switchable electric engine (DE 694 19 124 T2).
The disadvantage of this emergency brake comprises that in order to maintain the operating state here the electromagnet must be electrified at all times, which results in relatively high energy consumption.
Further a floating caliper disk brake is known, acting as the active brake, for a motor vehicle with a brake fastener, fixed at the vehicle, a floating caliper supported displaceable at the brake fastener, a brake actuator arranged on a brake disk side for the direct impingement of braking force to at least one brake pad, as well as a device for adjusting the clearance. The brake pad located axially towards the outside is pre-loaded via tension springs in reference to the floating caliper leg. An electric stroke magnet is used as the adjustment device for compensating clearance, showing a armature, connected to a tappet, via which the adjustment force developing when energizing the stroke magnet is transmitted to the brake pad. The application of the tensile brake force may occur electromagnetically (DE 101 57 324 A1).
Finally, a disk brake is known with an actuating device, which is coupled via a self-enhancing device to at least one brake pad. A brake caliper embodied as a floating caliper encases a brake disk as well as the brake pads arranged at both sides of said brake disk. The actuating device comprises a translationally acting electromagnet with a coil, which when being energized generates an actuating force applied at the coil core for tightening the disk brake. A spring applied rigidly at the vehicle acts upon the self-enhancing device in such a manner that it is pre-loaded by the force of the spring, opposite the primary direction of rotation of the brake disk, so that the spring counteracts the effect of the self-enhancement. Consequently, when the tensile force of the brake is reduced, for example when the brake operation is concluded, the disk brake is released by the force of the spring in the disengaging direction. This way, a precisely dosed adjustment of the tensile braking force is possible using only one coil acting in a translational fashion. For this purpose, a control device is used, which allows a targeted control and/or electrification of the coil (DE 102 01 607 A1). The disadvantage of this disk brake is given in that for applying the braking force always a self-enhancing device is necessary, i.e. the actuation device itself, in the present case the electromagnet acting in a translational fashion, cannot generate the braking force to be applied upon the brake disk. The solenoid plunger magnet used in the actuator only serves as a control magnet for the brake booster. Additionally, the application thereof is limited to such devices and arrangements, with their process of motion requiring to be controlled via braking processes due to frequently changing events and situations, which for example is necessary when driving a vehicle.